There's a common belief that, when you get married, your credit record will link up with your spouse's, thus creating a joint file. This is not the case, only joint credit will link you and your spouse together. Marriage alone is not enough to impact your credit rating.
Another common myth associated with marriage, is that once a partner changes their last name their credit history is erased, thereby restarting their file. This is false - your credit history will remain the same. The only difference to your file will be your new name, which will have been added as an alias. If you have recently entered into a marriage you will have to inform your creditors of this name change in order for it to appear on your file. Only then will your credit record change to reflect this.
Whilst marriage is not enough to link you and your partner's credit files, joint credit applications will make an association between you and your partner. The following three scenarios will create this link:
While this can be great for couples who have a solid financial history, if you or your partner has a background of defaults it can affect the other's file.
Even if your joint accounts are up to date and you have no current issue with debts, establishing a joint account with your partner will mean that they become a financial associate and will be named as such on your file. In this case, creditors may choose to look up your partner and their history could affect any future credit applications.
If you or your partner have a rocky credit history it might be best for you both to keep your finances separate and to work on rebuilding the credit file in need.